Question
I have a Quarter Horse gelding (11 years old, 16.3 hands) that is in light work a few days a week. I also show him occasionally in the warmer seasons. He is moderately thin with visible ribs. He spends 18 hours in a drylot with little to no pasture forage and 6 hours in a stall each day. He is fed 8 lb (3.6 kg) of high-fat feed daily and free-choice grass hay. The current feeding program works great until it gets extremely hot and humid, and then he just sweats off all of his weight, leaving him too thin.
Answer
Weight loss during hot weather can be due to fluid losses from sweating as well as decreased intake of both forage and feed. High-fat diets are thought to help reduce heat load, which can be beneficial in hot climates to help minimize heat stress. Dietary changes need to be made in combination with other management practices that offer a cool area with shade and airflow during the hottest parts of the day.
Increasing the amount of high-fat feed offered by 1-1.5 lb (0.2-0.7 kg) per meal should help maintain weight during periods of hot weather. If your gelding won’t eat the additional feed, a cost-effective way to increase the energy density of the ration would be to supplement with vegetable oil.
If the quality or quantity of grass hay consumed is a limiting factor, offering a small amount of leafy alfalfa hay each day can increase calorie intake and support weight gain. High-quality legume hays are generally well accepted by horses and can help increase voluntary feed intake.
If you can’t source high-quality alfalfa hay, then you may consider offering a mash made from alfalfa pellets. In addition to bumping up calorie intake, a mash will increase water intake and provide an easy way to feed electrolytes, which are depleted through sweating. Free-choice access to salt should be available with supplemental electrolytes added to the feed based on sweating rate.
One final thought: if you have access to lusher turnout, you might consider allowing him to graze in that paddock or pasture. Many horses that refuse feed and hay in hot weather will continue to graze, especially during the cooler hours of the day when insects are less active. Fresh pasture contains high amounts of moisture, which will help replenish water lost as sweat.
